Drizzle oil into a pan and add curry powder, ginger, shallot, garlic and chilli for few minutes or until they are aromatic.
Add chicken broth, oyster sauce, soy sauce, Chinese cooking wine, salt and sugar into the pan. Bring it to boil. Turn off the heat and strain stock through a fine mesh strainer into another bowl discarding the solids.
Return the sauce to a pan and add fish balls. Bring it to boil and cook for few minutes.
Mix cornstarch and water. Use cornstarch mixture to thicken the sauce.